Identifying Oxidizing and Reducing Agents in a Redox Reaction

Introduction

• Formation of sodium chloride from sodium metal and chlorine gas.
• Objective: Identify oxidizing and reducing agents.
• Prerequisite: Assign oxidation states.

Assigning Oxidation States

Sodium

• Elemental Form: Oxidation state = 0.

Chlorine

• Elemental Form: Oxidation state = 0.

Sodium Chloride

• Sodium Cation: Oxidation state = +1 (equals the charge on the ion).
• Chloride Anion: Oxidation state = -1 (equals the charge on the ion).

Analyzing the Redox Reaction

Sodium

• Oxidation state changes from 0 to +1.
• Conclusion: Sodium is oxidized.

Chlorine

• Oxidation state changes from 0 to -1.
• Conclusion: Chlorine is reduced.

Visualizing Oxidation States with Valence Electrons

• Representation of electrons as dots can aid in understanding oxidation states.
• Sodium: Normally has 1 valence electron, oxidation state = 0.
• Chlorine: Normally has 7 valence electrons, oxidation state = 0.

Products – Sodium Chloride Formation

• Sodium loses its valence electron forming a cation.
• Sodium: Oxidation state = +1 after losing electron.
• Chlorine: Gains one electron, oxidation state = -1.

Writing Half Reactions

Oxidation Half Reaction

• Sodium Atoms to Sodium Ions:
  • 2 Na → 2 Na⁺ + 2 e⁻ (Loss of Electrons)
  • Mnemonic: LEO (Loss of Electrons is Oxidation)

Reduction Half Reaction

• Chlorine Molecule Gaining Electrons:
  • Cl₂ + 2 e⁻ → 2 Cl⁻
  • Mnemonic: GER (Gain of Electrons is Reduction)

Combining Half Reactions

• Original reaction: 2 Na + Cl₂ → 2 NaCl

Identifying Oxidizing and Reducing Agents

Sodium

• Role: Reducing agent (supplies electrons for the reduction of chlorine).

Chlorine

• Role: Oxidizing agent (receives electrons from sodium, causing oxidation of sodium).

Conclusion

• Sodium is oxidized but acts as the reducing agent.
• Chlorine is reduced but acts as the oxidizing agent.
• Tip: Focus on electron transfer to understand agent roles.